Two useful sayings I found are truisms

[paulo21uk]

Everything that irritates us about others can lead us to an understanding of ourselves

and

When someone has been punching you in the face and then they stop, do you thank them for letting up or do you ask why they punched you in the first place?

 

[Baby Universal]

Good ones, here are a couple more.

Stop walking in to a room full of people and wondering 'Do they like me', and start walking in to that room and ask yourself 'Do I like THEM'

How people behave towards you is a reflection of the person they are, not who you are.